Fix wrong contentInsets for top-level child scroll views

The automaticallyAdjustsScrollViewInsets property makes a container view controller only look at the top level view. In the case of SDCSegmentedViewController, that view was not a scroll view, but a regular UIView. Since SDCSegmentedViewController is itself a container view controller, it should also adjust a top-level scroll view’s insets that it contains.
Add call to super
Use argument to remove observers
Adjust scroll indicators as well as scroll view content
Clean up and refactor
Update podspec